|Type 97 Mk 2 Nose Fuze - Navy|
The Type 97 Mk 2 Nose Fuze - U.S. Designation A-3(a) - is an updated and improved version of the Type 90.
This is found on wide variety of bomb types.
Color variations have been observed on the external body shaft. I've no information as to why that is, or what purpose the coloring is for (?).
When the bomb is released, the arming wire is pulled through the eyelet, breaking loose at the soldered points. This simultaneously imparts an initial rotation to the arming vane assembly.
In seven rotations, the arming sleeve rises up on the threads of the striker spindle and locks against the stop screw, arming the fuze. (The vanes stay attached.)
On impact, the entire cap assembly is drived in, breaking the shear wire causing the firing pin to strike the primer.
The base is threaded to accept a standard Japanese gaine.
This fuze series has several variations, but all have essentially the same function.